Alloy



1935- J. w. BOLTON ET AL 1,988,154

ALLOY Filed May 11, 1935 til Patented Jan. 15, 1935 UNlTED STATES PATENTOFFICE ALLOY corporation of Ohio Application May 11, 1933, Serial No.670,516

2 Claims.

Our invention relates to alloys and in particular to an alloy ofsilicon, nickel and copper, and to a method of treating such an alloy inorder to permit of its machining while maintaining its ultimate hardnessbeyond the limit of economic machining practice.

It is our object to provide an alloy which has high resistance to wear,high hardness, resistance to galling or seizing, high strength and amarked resistance to corrosion under conditions of high temperature,high pressure water, steam or air, and in the presence of corrosivematerials such as dilute sulphuric acid, as well as in the presence ofvarious alkaline substances, such as sodium hydroxide and sodiumcarbonate. 7

It is our object to provide such an alloy that has a good resistance tocorrosion of a wide variety of solutions.

It is a further object to provide an alloy that can be cast and heattreated so that it will have a relatively low hardness for machining orforming purposes and thereafter by heat-aging can be made to give aresulting high hardness.

It is our object particularly to provide an alloy that after the secondor aging treatment to increase itshardness, produces no scaling, nopronounced distortion and very slight shrinkage and therefore can beimmediately used with very little or no re-machining after the secondtreatment.

It is our object to provide an alloy particularly useful in valves forapplication to valve seats and disks and other structures whereinphysical characteristics embodied in this alloy may be employed withobvious advantage.

Referring to the drawing, Figure lillustrates a microphotograph of thisalloy of our invention prior to the first heat treatment.

Figure 2 represents a microphotograph subsequent to the first treatment.

Figure 3 is a microphotograph after the second heat treatment. I

Figure 1 shows the cast structure enlarged 50 diameters after havingbeen etched with nitricacetic acid plus a crystal of chromic acid. Theblack structure (marked 1) is the harder component rich in silicon whilethe softer background in white (marked 2) consists largely of thecopper-nickel solid solution.

Referring to Figure 2, it will be noted that as a resultof the firstheat treatment, there is a small amount of the black hard component 1with a marked. uniformity of structure which results in the workablecharacteristics hereinafter described. The magnification and the etchingdestroy the uniformity of the structure.

fluid are the same as that used in connection with Figure 1.

Referring to Figure 3, which has been treated with the same etchingfluid and has the same magnification as the other views, the effect ofaging at 1000 degrees on the structure in No. 2 is evident. There is amarked increase in hardness due to the increase in the hard blackcomponent 1, but this second heat treatment does not Thus the hardnessis increased, but the other qualities of the alloy are maintained.

We have found that this alloy should consist of from 1.75 to 3.25percent silicon, the balance being copper and nickel in approximatelyequal ratios.

We have found alloys of 1.75 to 2.75 percent silicon and the balance innickel and copper in approximately equal ratios, or 2 to 3.25 percentsilicon and the balance in-copper and nickel in approximately equalratios, to be excellent alloys for our purpose.

Small percentages of lead and phosphorus do not materially affect theproperties of our alloy and may be added to facilitate foundry and shopproduction.

Heretofore in the art the regular cupro-nickel alloy having copper andnickel of approximately equal amounts possesses the followingapproximate physical properties in the cast condition:

Tensile strength 50,000-60,000' Elongation 20-35% Brinell hardness -120We have found, however, that our alloy of silicon, nickel and copperpossesses the following physical properties in cast condition:

Tensile strength 90,000-125,000 Elongation 245% Brinell hardness 250-325After casting this alloy, we first soften the alloy by quenching in anysuitable medium such as air, water or oil from a temperature ofapproximately 1350 degrees to 1600 degrees Fahrenheit. We hold such atemperature for 45 minutes or more according to the requirements of heatpenetration and time necessary for partial re-sothat gives the mostsatisfactory hardness for machine work in the shop.

After the parts are machined, they are then subjected to an agingtreatment process at from 900 to 1200 degrees Fahrenheit forapproximate- 17 8 hours. The parts are then cooled in the air or in thefurnace as desired.

The result of this aging treatment is to recover or increase the initialhardness. Such recovered or increased hardness ranges from 275 Brinellup to as high as 360 Brinell. We also retain appreciable ductility as aresult of these treatments.

The exact properties desired can be secured by the use of thiscompcsition of alloy, first cast- 1 ing it, then heat treating it toincrease ductility and obtain reduction of hardness, machining it andthen recovering or increasing hardness by age hardening it withoutaffecting the machine work and without pronounced distortion, shrinkageor cracking. In short, the resulting product is ready for use, withpossibly a slight finish which sometimes is desired.

Other characteristics of the alloy of our invention are developed by theaddition of any one of the following to the alloy:

. Per cent (a) Manganese to (b) Iron 0 to 10 (c) Aluminum 0 to 5 (d) Tin0 to 5 (e) Zinc 0 to 5 (I) Phosphorus 0 to 1 (0) Lead 0 to 2 (h)Molybdenum 0 to 4 (i) Chrom O to 4 (i) Cobalt 0 to 4 (k) Vana 0 to 2 (l)Tungsten 0 to 3 (m) Tita 0 to 3 The addition of manganese toughens thealloy and lowers the quenching temperature. In some instances it lowersit about 200 degrees. This is desirable in certain types of castingsbecause the lower the quenching temperature, the less the possibility ofundue strain and possible cracking and also the finer the grain and thegreater the ductility.

The addition of aluminum lowers the strength somewhat but the hardnessremains'at approximately 320 Brinell.

The addition of iron within the percentage specified does not change thephysical properties. The addition of tin does not change the strength ofthe alloy but lowers the Brinell to about 286. The addition of zinclikewise lowers the Brinell about 50 points.

The use of lead improves the machinability of the alloy.

It will be understood that the resulting alloy such as described hereinhas the light silver or white color of alloys containing largepercentages of nickel and is only slightly darkened by the final heattreatment.

Under conditions which are extremely severe, as encountered by valveseats, disks and like structures, the alloy develops unique mechanicalproperties of resistance to galling or seizing, and high strength. It isproduced at a much lower cost than any material such as stainless steelof equivalent hardness and can be handled in a machine shop withoutdifilculty due to its controllable hardness.

It does not lose its hardness at working temperature as in valves of 500degrees, whereas such products as stainless steel will lose as much as50 points hardness under similar circumstances.

It will be understood that the reduction of hardness after the firstheat treatment of this cast alloy enables rapid machining on automaticor semi-automatic machine tools with accompanying economies ofproduction.

We find that the addition of the unusual amount of silicon as indicatedwithin the ranges indicated gives us the properties we desire and as wedepart from these ranges, the properties we desire begin to disappear.

It will be understood that we desire to comprehend within our inventionand the scope of the claims thereof such equivalent materials and Iproportions as may be found necessary to adapt this invention to thevarying conditions met in actual practice and we do not limit ourselvesto these specific materials and proportions.

Having thus fully described our invention, what we claim as new anddesire to secure by Letters Patent, is:

l. A new article of manufacture for use as an alloy which is ductile andwhich may be softened and machined without hot rolling after being heattreated comprising the combination of 1.75 to 2.75 percent silicon, thebalance being nickel and copper in approximately equal ratios.

2. A new article of manufacture comprising an alloy which is ductile andwhich may be softened and machined without hot rolling after beingheat'treated consisting of approximately 1.75 to 3.25 percent siliconwith nickel and copper in approximately equal ratios.

JOHN W. BOLTON. SYLVESTER A. WEIGAND.

